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(PS) is a computer language for creating vector graphics. It is a dynamically typed, concatenative programming language and was created by John Warnock, Charles Geschke, Doug Brotz, Ed Taft and Bill Paxton in 1982. It is used as a page description language in the electronic and desktop publishing areas.

OpenGL

an open source alternative to the OpenGL Utility Toolkit (GLUT) library. GLUT (and hence FreeGLUT) allows the user to create and manage windows containing OpenGL contexts on a wide range of platforms and also read the mouse, keyboard and joystick functions. FreeGLUT is intended to be a full replacement for GLUT, and has only a few differences.
Since GLUT has gone into stagnation, FreeGLUT is in development to improve the toolkit. It is released under the MIT License.

a cross-language, multi-platform application programming interface (API) for rendering 2D and 3D vector graphics. The API is typically used to interact with a graphics processing unit (GPU), to achieve hardware-accelerated rendering.

OpenGL is an API used for drawing 3D graphics. OpenGL is not a programming language; an OpenGL application is typically written in C or C++. What OpenGL does allow you to do is draw attractive, realistic 3D graphics with minimal effort. The API is typically used to interact with a GPU, to achieve hardware-accelerated rendering.

Color image pipeline

YUV

http://en.wikipedia.org/wiki/Yuv
> Y' stands for the luma component (the brightness) and U and V are the chrominance (color) components; luminance is denoted by Y and luma by Y' – the prime symbols (') denote gamma compression, with “luminance” meaning perceptual (color science) brightness, while “luma” is electronic (voltage of display) brightness.

Y'UV was invented when engineers wanted color television in a black-and-white infrastructure. They needed a signal transmission method that was compatible with black-and-white (B&W) TV while being able to add color. The luma component already existed as the black and white signal; they added the UV signal to this as a solution.

Image file formats

JPEG

The most common filename extensions for files employing JPEG compression are .jpg and .jpeg, though .jpe, .jfif and .jif are also used. It is also possible for JPEG data to be embedded in other file types – TIFF encoded files often embed a JPEG image as a thumbnail of the main image; and MP3 files can contain a JPEG of cover art, in the ID3v2 tag.

Exif

Exif Orientation Tag

I found that I'm in agreement with Dave Perrett. For me, the orientation tag was causing unpredictable rotations as I moved images around different systems and software, so I looked for a way to identify the tag, and then to clear or reset it to a harmless state.

MSWIn

exiftool-9.xx.zip extracts just the Stand-Alone Executable: exiftool(-k).exe. Just drag and drop an image file, or several, onto it. The file(s) don't move, but instead a console window pops up, and fills up with all the exif info found - which is usually a lot. Alternatively, work from the MSWin Console, like this:

exiftool -Orientation *

- to see the Orientation tag settings for all files in the current folder.

Orientation

Rename the Windows executable to exiftool(-k -Orientation).exe and drag an image file onto it - you'll see only the value of the orientation tag displayed in the popped-up console. Something like:

Orientation: Rotate 90 CW

Rewrite Orientation to Horizontal:

This is my preferred way to render the Orientation tag harmless. Then I manually rotate images, knowing that there's never going to be any further confusion as they're passed on to other viewing tools.

Rename the executable thus: exiftool(-Orientation=Horizontal).exe

Can drop a load of images onto it at one go.

The image.type is renamed to image.type_original, and then a new image.type is written in the folder with its Orientation tag set to Horizontal. If all is okay (it always is) delete the originals.